I think that when things get out of your control, you can (1) accept that you are not in control, (2) try to steer yourself away from the effects of the things that are out of your control, and(/or?) (3) not think about the things that are out of your control.

So what does that mean? Well, your fridge not working and the repairman's schedule are out of your control. That is just how it is, and you can't really do anything about it. What you can do is to try to re-schedule and change your own plans to best accommodate the uncertain things (for example: making your plans for evenings when the repairman is unlikely to work, limit your need for a fridge by eating outside or staying at your friend's place if possible, etc.): Find ways to limit the negative effects.

As for the not thinking about it part... well, that's not always easy. But doing something you really like usually helps at least a bit. For me, nowadays, that would be either exercising or listening to music. For you? Reading, maybe? Or going for a walk/jog? And if breathing exercises help with the stress, then definitely do them too.